For the crushing (granulating) of mineral, vegetable or embrittled materials among others, beater mills (hammer mills) are used, the stationary crushing path of which is equipped with wear plates and striking bars, which are received between corresponding pressure plates. Wear plates and striking bars must be replaced frequently, if the desired grain size is supposed to be held within a range of variation which is as narrow as possible. This is also true, even though to a lesser extent, for the pressure plates on both sides of the striking bars.
From the chip-wood industry has become known according to German Pat. No. 33 09 517 a method and an apparatus for carrying out said method, in which the steel strip knives in use are replaced during apparatus operation continuously or periodically with sharp steel strip knives. According to experience, flakes (flat chips) of an always constant quality and form thus are produced from chips. The previously needed machine idle time for the replacement of dulled knives is hereby no longer needed.
However, for the granulating of mineral, vegetable or embrittled materials a method modified according to said German Pat. No. 33 09 517 does not present a satisfactory solution, because not only do the edges of the striking bars dull quickly, but so also do the counterlips of the wear plates which lie close adjacent the inside of the striking bars and, even though to a reduced degree, so also do the wear surfaces of the pressure plates located on both sides of each of the striking bars, which wear surfaces face the beater shoes of the rotor.
The purpose of the invention is to provide a method for the granulating of mineral, vegetable or embrittled materials and an apparatus which serves to carry out said method, with which constant grain sizes can be produced at all times during uninterrupted mill operation.
The invention attains this purpose with a method, in which the wear plates of the stationary crushing path and the striking bars then in use (and, if desired, pressure plates arranged on both sides) are replaced during mill operation continuously or periodically with new (replacement) parts of the same types. Replacement wear plates and striking bars (and their pressure plates if desired) are thus each stored in corresponding magazines on the new part input side of the beater mill, from where they are fed by cylinder-operated slide members to the crushing path. Suitable means such as simple magazines may be used on the worn part discharge side of the beater mill for receiving the worn wear plates and striking bars (and, if desired, the worn pressure plates). Corresponding with their differing wear it is possible to move the wear plates and striking bars (and, if desired, the pressure plates) at different feeding rates through the stationary crushing path. It is hereby possible to load the wear plates and striking bars on the mill's input side more heavily with granulatable material than on the mill's discharge side, in order to compensate for the fact that the mentioned wearable parts wear more the longer they are used in the crushing chamber. Such a different loading with granulatable material can be achieved by a correspondingly sloped position of the beater shoes or, in the case of a beater mill with a horizontal axis, by sloped positioning of said axis.
In a preferred embodiment of the inventive apparatus, wear plates and striking bars are manufactured of thin steel strips incorporating longitudinal grooves which are all identical in form. Each striking bar is held by at least one pressure plate, or if desired by two pressure plates between which the striking bar is tightly clamped. In order to require as little part advancing force as possible during the periodic advance, all pressure plates can be simultaneously released from their striking bars prior to a feeding (part advancing) cycle by movement of a suitable center tension ring, similar to the suggestion in German Pat. No. 24 36 316. However, a center tension ring is not needed if the striking bars are each clamped fixedly between two pressure plates and are moved therewith continuously or periodically through the stationary crushing path. The running surfaces of the pressure plates, which running surfaces face the beater shoes, can be designed in a conventional manner to be regrindable and readjustable.
In the inventive method for continuous granulating of mineral, vegetable or embrittled materials, for the first time the factors "crushed particles quality", "wear part use" and "energy consumption" are presented in a preselectable relationship and thus optimized, whereby furthermore the previously needed idle mill times ("down time") for the replacement of the worn parts, no longer exist.